Brett Cannon: Unravelling the `pass` statement

This is the next past in my series on Python&aposs syntactic sugar. It&aposs unfortunately been a while since my last post due to Python 3.10 and PyCon US 2021 taking up a lot of my time. But with those no longer being a distraction, I can get back into a rhythm of doing posts, so I&aposm going to do probably the easiest bit of Python syntax that I can unravel: pass.

The definition for pass is extremely simple:

pass is a null operation — when it is executed, nothing happens.

That means pass does as much as "pass" or 42 does on their own: absolutely nothing but take up a line of syntax.

The reason pass even exists is so that you can syntactically signal that something is purposefully empty versus accidentally leaving something out. For instance, in the following if statement:

if x:
    pass
else:
    "pass"

Example of if statement is do-nothing branches

In the first block you know for certain that nothing is supposed to be there. But in that second block using "pass", you can&apost be certain that the line was actually supposed to be y = "pass" or any other valid use of the "pass" string.

While it&aposs easy to replace pass syntactically, it does provide a simple yet useful bit of semantics.

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